FileSystem Monitoring - Threshold 85%

#!/bin/bash
# set usage alert threshold
THRESHOLD=85

#hostname
HOSTNAME=$(hostname)

#mail client
MAIL=/bin/mailx

# store all disk info here
EMAIL=""

for line in $(df -hP | egrep '^/dev/' | awk '{ print $6 "_:_" $5 }')
do

        part=$(echo "$line" | awk -F"_:_" '{ print $1 }')
        part_usage=$(echo "$line" | awk -F"_:_" '{ print $2 }' | cut -d'%' -f1 )

        if [ $part_usage -ge $THRESHOLD -a -z "$EMAIL" ];
        then
                EMAIL="$(date): Running out of diskspace on $HOSTNAME\n"
                EMAIL="$EMAIL\n$part ($part_usage%) >= (Threshold = $THRESHOLD%)"

        elif [ $part_usage -ge $THRESHOLD ];
        then
                EMAIL="$EMAIL\n$part ($part_usage%) >= (Threshold = $THRESHOLD%)"
        fi
done

if [ -n "$EMAIL" ];
then
        echo -e "$EMAIL" | $MAIL -s "Alert: Partition(s) almost out of diskspace on $HOSTNAME" "test@test.com test1@test.com"
fi